The invention relates to the shearing of heavy wall tube stock through the use of a pair of exterior dies, one of which moves in an orbital path with respect to the other with a pair of mandrel dies located within the tubing which move in a like motion.
The general concept of shearing tubing by orbital movement of one die member relative to a stationary die is known in the prior art as taught in the following U.S. patents:
U.S. Pat. No. 1,216,426 to Erickson PA1 U.S. Pat. No. 3,494,233 to Kojima PA1 U.S. Pat. No. 3,657,951 to Clark PA1 U.S. Pat. No. 4,003,279 to Carmichael. PA1 U.S. Pat. 1,280,199 to Erickson PA1 U.S. Pat. 4,059,036 to Hartley
The patents listed teach a variety of adjustable eccentrics or dual eccentrics as typified by Kojima.
The use of a two-piece mandrel in tube shearing has also been generally taught in the following U.S. patents:
and the previously mentioned patents to Kojima, Clark and Erickson (U.S. Pat. No. 1,216,426). Some of the mandrels are of the expandable type such as Hartley, while others are loose-fitting fixed-diameter types.
The quality of the sheared surface, or in other words the distortion caused by the shearing action is effected by the degree of fit of the mandrel sections in the tube being cut and the adjacent exterior dies. In the above-mentioned patent to Kojima (U.S. Pat. No. 3,494,233) the mandrel parts, as shown in FIG. 5, have a loose fit within the inside diamter of tube and also their edges are not accurately positioned at the shearing plane of the tube, all of which promotes a greater amount of deformation or burr at the cut edge of the tube.
The present invention provides a sheared edge surface on relatively thick-walled tubing which is relatively free of distortion and burr when compared with the prior art methods mentioned above. To achieve this, applicant's mandrel has a fixed-diameter close-fitting tolerance with the inside diameter of the tube stock. Therefore the removal of the mandrel after the tube is cut becomes more difficult by reason of the increased possibilities of the mandrel hanging up in the section of tube stock just cut. At some time during the angular rotation of the orbiting die cut, the tube length being cut will shear free from the stationary length of tubing while the orbiting die continues to rotate through a full 360.degree. revolution. If the tube mandrel die sections are slightly out of alignment concentrically, the outside die section will hang up on the piece of tube and the ram will be unable to remove the mandrel. Located inside the second section of the mandrel is a large elastic ring which snugly fits on the ram diameter so that whenever the outside lateral forces are removed from the mandrel, the resilient or elastic ring brings the second mandrel section back into concentric alignment with the first section permitting easy removal of the extendable ram.
The tube-cutter of the present invention also incorporates a tube-stop apparatus which accommodates the wobble cutting action of the movable die and thereby prevents the section of tube being cut from jamming between the tube stop and dies. This is accomplished by providing a stop member which although it does not move longitudinally in the apparatus is free to move laterally with the orbiting die during the eccentric cutting movement. This jamming problem becomes more pronounced with thicker wall tube being cut in relatively short lengths.
It is therefore the principal object of the present invention to provide an improved wobble-type cut-off machine which provides constant length sections with a minimum amount of tube deformation.
Another object of the present invention is to provide a high speed cutting apparatus which leaves a relatively clean edge.
Another object of the present invention is to provide a wobble-type cut-off machine for heavy wall tube which has a tube stop which permits the tubing being cut to move with the orbiting die.